Various medium access control (MAC) techniques for a sensor network have been developed according to service requirements. In particular, the IEEE802.15.4 MAC/PHY standards have substantially, widely been used as international standards. The IEEE802.15.4 MAC/PHY standards have an advantage of being easily developed and installed since they can reduce power consumption and have a simple construction. As representative examples, there are a contention-based MAC method based on a carrier sense multiple access/collision avoidance (CSMA-CA) method, and a restrictive GTS (Guaranteed Time Slot) method (a kind of TDMA) that is an optional technique.
A GTS mode defined in the IEEE802.15.4 MAC standards may be used as a sensor network MAC technique for realizing a telematics service in real time and with high reliability. However, in the GTS mode, it is difficult to collect and process data in real time and within a limited amount of time since the total number of GTS slots is limited to seven and only a PAN(Personal area network) coordinator can allocate GTS slots.